Integrating Control of Botrytis and Powdery Mildew in a Greenhouse Crop Progress Report — August 1995
Date 8/30/95
Title of Project Integrating Control of Botrytis and Powdery Mildew in a Greenhouse Crop
Institution where work is being conducted Michigan State Univ., Cornell Univ., Texas A&M
Amount of Endowment Grant $12,000
Covering Period 1/1/95 to 12/31/95
Anticipated Date of Project Completion/Final Report 12/31/96
Individual(s) Conducting Project:
(List Project Leader First)
Dr. Mary K. Hausbeck - Title Assistant Prof.
Telephone Number (517) 355-4534
Ms. Margery Daughtrey - Title Senior Ext. Assoc.
Dr. Larry Barnes - Title Associate Prof.
Integrating Control of Botrytis and Powdery Mildew in a Greenhouse Crop
M.K. Hausbeck, Margery Daughtrey , and Larry Barnes
- Project Objectives:
- 1) Develop a scouting program for PM and Botrytis blight;
- 2) Develop an
effective fungicide spray program for PM and Botrytis blight;
how the environment affects infection and disease development;
with that determined for PM into an integrated disease management system that utilizes samitation, fungicide
applications, and environmental manipulation to reduce disease incidence and severity;
entitled “Foliar Disease Management for Poinsettias”.
State University on poinsettias in full color. Fungicide sprays were initiated soon after the first appearance of
powdery mildew colonies on bracts. While growers would certainly want to avoid a situation where powdery
mildew has progressed to the bracts as in this study, this particular system works well in research to determine
the ability of fungicides to control disease.
2 applications), and all other fungicide treatments were applied at 7-day intervals (a total of 3 applications). At
the end of the experiment, colonies on two randomly identified bracts were counted to deterrmne whether the
fungicide treatments had provided effective control. Powdery mildew was best controlled by applications of
either Chipco 26019 WDG 50 WG (1.0 or 2.0 lb/100 gal) or the higher rates of Terraguard 5OW (16-4-4 or 16-8-8 oz/100
gal for the first, second, and third applications) or Cleary’s 3336 WP 5OWP (1.5 lb/100 gal). Since
there was no difference between the Chipco 26019 rates investigated in this study, the lower rate of 1.0 lb/100
gal could be expected to provide the same level of control as the higher rate of 2.0 lb/100 gal. Likewise, the lower
rates of Terraguard 5OW (16-4-4 oz/100 gal) were as effective as the higher rates of Terraguard 50W (16-8-8
oz/100 gal). However lowering the Terraguard 5OW rates further to 8-4-4 oz/100 gal was not equally effective
as the higher Terraguard rates used in this study.
fungicide application. This is why powdery mildew must be controlled early in production and removal of
infected leaves, if feasible, is helpful. The fungicides used in this trial were evaluated for their ability to prevent
the further development of powdery mildew beyond that existing prior to the first application of fungicide.
finishing or postharvest production phase. To evaluate the length of time fungicides can provide protection
against powdery mildew, plants were maintained for 56 days beyond the last fungicide application in a
greenhouse full of poinsettias that were heavily infected with powdery mildew. Fungicides were evaluated based
on their ability to suppress production of coradia (sporulation) in colonies on bracts and foliage, In this study,
42 days appeared to be the longest duration of control available beyond the last application from the fungicides
evaluated in this study. None of the powdery mildew colonies were active 42 days after higher rates of
Terraguard 5OW (16-4-4 oz or 16-8-8 oz/100 gal, a total of 3 sprays) were applied following disease detection.
It was interesting that when healthy plants were treated with Terraguard 5OW (4 or 8 oz/100 gal, a total of 4
applications) prior to exposure to powdery mildew, protection lasted for 42 days. Good control was also obtained
42 days after the last application when Chipco 26019 5OWG (1 or 2 lb/100 gal) or the lower rate of Terraguard
5OW (8-4-4 oz) was used after the detection of powdery mildew. When a low rate of Teffaguard 5OW (2.0
oz/100 gal, a total of 4 sprays) was applied prior to exposure to powdery Mildew, good control was obtained for
42 days. Although colonies for all treatments were active 5 6 days after the last fungicide treatment, control was
still obtained for the “best” treatments described at 42 days in comparison to the untreated control.
Texas will conduct additional studies on fungicide
efficacy in controlling PM and Botrytis blight on poinsettias including: Baking Soda, Bayleton/Strike, Chipco
26019, Cleary’s 3336/Domain/Fungo Flo, Daconil, Dithane T/O, Eagle, Milban, Oil/Sunspray, Ornalin, Phyton
27, Pipron, Protect T/O, Zyban, Rubigan, Soap (Mycogen’s 1446), Sulfur, Terraguard, Triforine, and Zineb.
